Arduino Nano - Uno as programmers.

Hey guys :slight_smile: !
I'm deciding between which Arduino board should I buy: Nano 3.0 or Uno R3.

It's very likely that I will use the board as an ISP programmer (bootloading/programming Arduino boards, Atmega chips on a breadboard, etc.)...
The problem lies on whether both of them can perform this kind of tasks.

I'm also planning on making some projects that will require PC communication as well as external power; and as far as I'm concerned, Arduino Nano can't use the USB connection if it's being powered externally, while Arduino Uno can.
Is there a possibility of powering the Nano externally and operate the USB port at the same time?

Thank you!

It's very likely that I will use the board as an ISP programmer

You will find that most Arduinis can be used for USP ISP programming, but some just seem to be easier. I recommend the UnoR3 with the Adafruit ZIF shield...

Ray

If you are not sure, use an Arduino Uno. That is the most standard Arduino board.

There is some confusion about the power for the usb chip.
I have a Nano clone from Ebay which works with usb and external power. As far as I know, also the Nano board V3 works without problem.
The sentence about it not being powered with external power is for older versions.
http://arduino.cc/en/Main/arduinoBoardNano

tfmToto:
Hey guys :slight_smile: !
I’m deciding between which Arduino board should I buy: Nano 3.0 or Uno R3.

It’s very likely that I will use the board as an ISP programmer (bootloading/programming Arduino boards, Atmega chips on a breadboard, etc.)…
The problem lies on whether both of them can perform this kind of tasks.

I’m also planning on making some projects that will require PC communication as well as external power; and as far as I’m concerned, Arduino Nano can’t use the USB connection if it’s being powered externally, while Arduino Uno can.
Is there a possibility of powering the Nano externally and operate the USB port at the same time?

Thank you!

The Nano CAN use USB connection while powered externally, the FTDI chip gets it’s power from the same Vcc bus that the 328P chip does. The Nano uses simple diode isolation between the the USB +5vdc and the on-board +5vdc regulator, if both are present then the one with the higher voltage will supply the board’s current.

The only significant differences between the Nano and Uno are:
Form factor, the Nano does not mechanically support shields.
Type of USB chip used requires different PC USB driver file.

I’ve burned the Uno bootloader onto my Nano 3.0 and it works fine, needing only to select the Uno type board from the IDE selection menu.

I looked at the schematic, and version 3.0 should be fine. But to be 100% sure, you have to test it.

I have used breadboards, Nano board and Uno board. The best way for me was to make a shield instead of a complete module. A shield can be placed on a Uno, Leonardo or Mega board. During development, things do go wrong, and it is easier to repair and continue with a shield.

I have personally used my Nano 3 to program ATmega328 and ATtiny85 using the ArduinoISP sketch. Like you, I prefer breadboards to shields for developing new projects.

However, my USB sockets are all 2.0, so no problems providing enough current. My PC runs Ubuntu rather than Windows, and I have had no problems with drivers, it just worked.

Paul

tfmToto:
Thank you for your answers.

I prefer wiring and building modules apart rather than using Shields.
The problem is that my PC's USB ports don't provide too much current., that's why I need to power the board externally.

The Arduino Nano can be powered via the Mini-B USB connection, 6-20V unregulated external power supply (pin 30), or 5V regulated external power supply (pin 27). The power source is automatically selected to the highest voltage source.
The FTDI FT232RL chip on the Nano is only powered if the board is being powered over USB. As a result, when running on external (non-USB) power, the 3.3V output (which is supplied by the FTDI chip) is not available and the RX and TX LEDs will flicker if digital pins 0 or 1 are high.

I don't fully understand the meaning of it: Will the USB connection work while being powered externally?
I know that Uno has no problems as it Power phase & USB Connection works completely different. I just want to make sure that Nano will do well too.

The statement in bold is simply wrong. The USB serial link on a Nano will work even if the board is powered from an external source.

Lefty

tfmToto:
I don't fully understand the meaning of it: Will the USB connection work while being powered externally?

I'm not surprised (that you aren't following it); the schematic appears to have some blunders on it.

Without examining my Nanos in detail (which I may do later), the suggestion is that you have two areas; the USB interface and the main chip. There is a Schottky diode feeding power from the USB connector which directly powers the USB interface, to the main chip and "Vcc" connections. There is also a regulator from "Vin" powering the Vcc connection, not the USB.

If there is no other source of Vcc, the Schottky diode will feed USB power to the main chip. If you power the main chip from an alternate source, it will not feed power back to the USB interface. This is precisely as it should be, if the USB is not powered, it is clearly not plugged in, not functional and it would be inappropriate to power up the interface chip. The diode also removes any safety concern about interference between an external power source and the USB connection - the USB interface will always derive its power from the USB connection and only that connection.

Paul__B:

tfmToto:
I don't fully understand the meaning of it: Will the USB connection work while being powered externally?

I'm not surprised (that you aren't following it); the schematic appears to have some blunders on it.

Without examining my Nanos in detail (which I may do later), the suggestion is that you have two areas; the USB interface and the main chip. There is a Schottky diode feeding power from the USB connector which directly powers the USB interface, to the main chip and "Vcc" connections. There is also a regulator from "Vin" powering the Vcc connection, not the USB.

If there is no other source of Vcc, the Schottky diode will feed USB power to the main chip. If you power the main chip from an alternate source, it will not feed power back to the USB interface. This is precisely as it should be, if the USB is not powered, it is clearly not plugged in, not functional and it would be inappropriate to power up the interface chip. The diode also removes any safety concern about interference between an external power source and the USB connection - the USB interface will always derive its power from the USB connection and only that connection.

I think you need to review the schematic a little more closely.

The 328P is powered via it's Vcc pin(s) and they are wired to a trace called +5V. The FTDI chip is powered by it's Vcc pin and is wired to the same trace named +5V. Bottom line is that if the 328P chip has power then so does the FTDI chip, no matter if the USB cable is plugged into a PC or not. Certainly the FTDI function will not work it it's not cabled up to a PC via the USB cable, but it's not because the FTDI chip has no power, It's powered anytime the 328P is powered.

Lefty

retrolefty:
I think you need to review the schematic a little more closely.

No, I’m not quite that blind!

I was choosing to believe the description page - more fool me - rather than the schematic, on the supposition that they could not have been so perverse as to power the FTDI in this fashion (preventing the board from being able to be put into a low power mode).

So I have verified it on my (clone) Nano. Really! If you must clone something, why could you not at least correct the blunders?

The only argument I can think of for not feeding the FTDI chip from the USB supply is that the serial communications code will put a “mark” on the Tx port and be sourcing up to 5 mA into the FTDI chip if it is un-powered, or that said code will be compromised by a break signal on the Rx port. I suspect however that this is less than the current drain of an idle FTDI chip anyway, so that argument would be moot.

And yet again, the Arduino reference pages prove to be simply directly misleading. :roll_eyes:

tfmToto:
Thank you for your answers.

I prefer wiring and building modules apart rather than using Shields.
The problem is that my PC's USB ports don't provide too much current., that's why I need to power the board externally.

One approach is to use a powered USB hub that sits between your computer and your microprocessor. This USB hub that Adafruit sells can deliver up to 2 amps to your board (by design, most computers will only deliver at most 0.5 amps): USB 2.0 Powered Hub - 7 Ports with 5V 2A Power Supply : ID 961 : $27.50 : Adafruit Industries, Unique & fun DIY electronics and kits

If you need even more power, this hub designed for the Raspberry Pi can deliver 3 amps (R-pi's tend to need a lot more juice than Arduinos with 0.7 - 1 amp normal): PIHUB - USB Hub for Raspberry Pi with US Power Adapter : ID 1516 : $34.95 : Adafruit Industries, Unique & fun DIY electronics and kits